Inkjet printers are well known and extremely popular. Details of a particular inkjet printer are described in U.S. Pat. No. 5,648,806, entitled Stable Substrate Structure for a Wide Swath Nozzle Array in a High Resolution Inkjet Printer, by Steven Steinfeld et al., assigned to the present assignee and incorporated herein by reference.
An inkjet printer ejects fine droplets of ink onto a print medium, typically paper, in response to electrical signals generated by a microprocessor. A typical inkjet printhead has an array of precisely formed nozzles overlying a printhead substrate. The substrate incorporates an array of firing chambers (or drop ejection chambers) that receive liquid ink through ink channels connected to one or more ink reservoirs. Each firing chamber typically has a thin-film resistor or a piezoelectric element which, when energized, causes a droplet of ink to ejected through an associated nozzle onto the medium as the printhead scans across the medium. Energizing a thin-film resistor heats the resistor to vaporize a portion of ink in the firing chamber to cause a droplet of ink to be ejected from its associated nozzle. Energizing a piezoelectric crystal causes the crystal to expand to propel a droplet of ink from a nozzle.
High quality color inkjet printers include printheads for the three primary color inks, cyan, magenta, and yellow, and a separate printhead for black ink. One type of color inkjet printer incorporates a separate replaceable print cartridge for each of the four colors of ink installed in a scanning carriage. Another type of color inkjet printer incorporates two, three, or four different color printheads in the same print cartridge. Still another type of color inkjet printer uses a single printhead (having a single substrate), having multiple sets of nozzles, that ejects a different color ink (e.g., CMY) through each set of nozzles. Some color printers use more than four colors of ink, with a separate printhead for each color. The order of printheads in the carriage is typically black on the left side or right side of the primary color cartridges, with the order of the primary color cartridges being arbitrary.
A common black ink is a pigment-based ink where undissolved particles are suspended in a clear solution. Such pigment-based ink creates the darkest black with a minimum of bleed into the paper. Since the paper is typically white, any significant bleeding of the black ink into the paper will noticeably reduce the sharpness of the edges of black text or other black print.
For color inks, dye-based inks are very popular. Dye-based inks do not have color particles suspended in solution and thus tend to bleed into the paper more than pigment-based inks. This bleeding is not noticeable due to the relatively low contrast between the white paper and the color ink. Since the dye-based ink wicks or bleeds into the paper, the dye-based inks dry faster than the pigment-based black inks, which effectively pool on the paper surface. Color inks may also be pigment-based.
Examples of such black inks and color inks are described in U.S. Pat. Nos. 5,695,820 and 5,626,655 assigned to the present assignee and incorporated herein by reference.
As inkjet printers evolve to print faster, there is less time for the ink to dry. In some cases, after printing on a page is complete, the printer needs to hold onto the page for a predetermined time in order to let the ink dry before depositing the page in an output tray. The drying of the black ink is likely to be the bottleneck for drying time of a page.
What is needed is a technique for reducing the drying time of inks deposited by an inkjet printer.